Use a mocked compositor for unit tests

ui/gfx/test/gfx_test_utils.cc

Index: ui/gfx/test/gfx_test_utils.cc
diff --git a/ui/gfx/test/gfx_test_utils.cc b/ui/gfx/test/gfx_test_utils.cc
new file mode 100644
index 0000000000000000000000000000000000000000..1b80d340f67ae4525047a76d9dee949ba842e85d
--- /dev/null
+++ b/ui/gfx/test/gfx_test_utils.cc
@@ -0,0 +1,35 @@
+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "ui/gfx/test/gfx_test_utils.h"
+
+#include "base/command_line.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include "ui/gfx/gl/gl_switches.h"
+
+#if defined(VIEWS_COMPOSITOR)
+#include "ui/gfx/compositor/compositor.h"
+#include "ui/gfx/compositor/test_compositor.h"
+#endif
+
+namespace ui {
+namespace gfx_test_utils {
+
+void SetupTestCompositor() {
+#if defined(OS_LINUX)
+  // Test bots don't have DesktopGL/EGL.
+  EXPECT_TRUE(!CommandLine::ForCurrentProcess()->HasSwitch(switches::kUseGL));

[Paweł Hajdan Jr., 2011/10/19 08:49:37]

Please convert it so that the function returns bool and uses WARN_UNUSED_RESULT.
This makes it easier to propagate failure info up.

[danakj, 2011/10/19 13:55:48]

So if you have GL set to something already the test is not going to work on
Linux.  I believe the test should just fail at this point, because this is a
finding a conflict in the code.  And I don't see you handling this with some
sort of fallback path, do you?

+  CommandLine::ForCurrentProcess()->AppendSwitchASCII(
+      switches::kUseGL, gfx::kGLImplementationOSMesaName);
+#endif
+
+#if defined(VIEWS_COMPOSITOR)
+  // Use a mock compositor that noops draws.
+  ui::Compositor::set_compositor_factory_for_testing(
+      ui::TestCompositor::Create);
+#endif
+}
+
+}  // namespace gfx_test_utils
+}  // namespace ui